Forest Investment Account (FIA) - Forest Science Program
FIA Project Y071169

    Regeneration under different partial cut silvicultural systems
Project lead: Larson, Bruce
Contributing Authors: Larson, Bruce C.; Amoroso, Mariano
Imprint: [BC] :, 2007
Subject: Forest Investment Account (FIA), Forest Reproduction, British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Our goal is to help in the design of partial cuts harvests to produce the most desirable light conditions for regeneration. Partial cutting for the renewal of evenage forests using natural regeneration is a common practice throughout the world. Mounting social pressures in BC against clearcutting has led to great interest in partial cutting. In many areas this cutting has taken the form of variable retention with vague intentions of how long the retained trees will be maintained rather than concerted efforts to maintain the productive evenage nature of the forest stands while meeting visual goals through partial cuts. With the use of partial cutting the contribution of natural regeneration is often left to chance, merely to be monitored in regeneration surveys after the cuts. Planting in the openings has been used to ensure regeneration success and meet legal requirements, but the actual planting needs are based on the best estimation of the manager. Workshops held throughout the Province by FERIC in 2004 indicated that if overstory retention was 50% or less (as measured by basal area) adequate natural regeneration was achieved to meet stocking objectives. These workshops (which included results from many trials including Sicamous Creek, MASS, EMEND, and others) all concluded that, although other growth factors such as moisture affected the actual outcome, the overriding environmental factor affecting success was light. Most trials have been in other regions, except Sicamous Creek which is in the ESSF zone of the Southern Interior. A range of different silvicultural systems have been established at the Alex Fraser Research Forest (AFRF) (particularly in the transition area between the SBS and the ICH zones) since the early 90ís as part of demonstration and research. These trials were established to investigate the effect various types of partial cutting have on the recruitment and subsequent growth of regeneration. Silvicultural systems used consist of many different types including various shelterwood systems (uniform, irregular and strip), patch cuts, and expanding groups. These cuts have been operational in nature, but all represent trials and demonstrations and have been monitored as such. A few blocks have had more detailed research and field measures. We propose to analyze the development of natural regeneration in four types of cutting: uniform shelterwood, irregular shelterwood, strip shelterwood, and expanding group cuts. The cuts were carried out between 1992 and 2005, but the majority have been since 2000. All of the cuts we will use have had regeneration surveys and been found to have sufficient regeneration. A couple of the older cuts have been the site of previous research and have detailed data on regeneration growth. There are enough different blocks of each treatment that we will have suitable replication. Based on the conclusions of the various researchers expressed at the FERIC workshops we will concentrate on light effects (Williams et al., 1998). We will use the site ranking system established by Klinka et al. (2004) for the AFRF to adjust for site differences between blocks; this will allow us to account for differences in site conditions such as site index, slope, aspect, and prevent confounding effects among treatments. We will measure the age, size, and current increment (height) of the natural regeneration by species in the different treatments. We will do this by using small plots along transects that cross the openings. At each plot we will take a hemispheric photo so the light conditions can be estimated. Another important aspect of the study will be to asses the growth of planted seedlings using the same light measures. The planted seedlings will serve as a 'bioassay' of the different growth factors in our measurement plots. In addition we will assess the growth of non-tree species that compete with the tree regeneration. We will be able to assess how light and the other growth factors influence their heights. The success or failure of natural regeneration under different types of partial cutting is driven by the microsite light conditions throughout the cut area. These light conditions will dictate seedling growth, as well as the growth of competition. The effect of light will be modified by the amounts of other growth factors on site. In this study we will investigate these relations and quantify the effects.
Contact: Larson, Bruce, (604) 822-1284,


Executive summary (23Kb)

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Updated August 16, 2010 

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